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Homework Help: Linear algebra vectors

  1. Mar 15, 2009 #1
    1. The problem statement, all variables and given/known data
    F and G are not 0.
    F and G are parallel
    Proof that F X G is=0

    Attempt for a sol:

    But then I don´t know how to show that they are parallel.


    Find some numbers for F and G that I know that makes them parallel and show that FXG
    But I think I´m not supposed to use numbers, but a,b,c...

    Would you use either one of theses attempts or not?
  2. jcsd
  3. Mar 15, 2009 #2


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    Science Advisor
    Homework Helper

    There are several different definitions of vectors being parallel (one of them is that the outer product is zero).
    So can you check your notes / textbook and tell us what it means if two vectors are parallel.

    If it says something like: "F and G are parallel if there is some number c such that F = c G" then you can simply take
    F = (x, y, z)
    G = (cx, cy, cz)
    and compute the cross product.

    (Note that this is completely general because the cross product only exists in 3 dimensions)
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